1. Field of the Invention
The invention pertains to the field of control of structural performance of load-bearing components. More particularly, the invention pertains to control of structural performance of load-bearing components through strength-altering, friction stir processed patterns.
2. Description of Related Art
Mechanical components in machines carry load in various modes, such as bending, torsional, and axial modes. It is customary in mechanical design to tailor the geometry of a component to best accommodate load, for example, by increasing a section of a beam in proportion to the bending moment so that stress is constant along the length of the beam. It is also possible to vary the material properties over the dimension of a component to achieve the performance required of the component.
An important design consideration for a variety of machines is the capacity to dissipate energy in the event of an impact. In this situation, it is desirable to have all the products of a given design perform in a highly repeatable manner. For example, energy-absorbing elements of a vehicle must deform the same way from vehicle to vehicle for there to be confidence that vehicles provide consistent crash-worthiness. Achieving this goal is more difficult under some loading modes than others.
When loads are carried in a compressive axial mode, a component is subject to buckling, making repeatability more difficult to achieve. In this case, the deformation behavior is strongly influenced by the location of small imperfections, unless some geometric feature is intentionally introduced in the design. Often, this is accomplished through the details of the part shape. However, intentionally altering the material's strength in some areas of a component can provide the same benefit.